The present invention generally relates to a sputtering target having mainly oxychalcogenide containing La and Cu, and particularly to a sputtering target having at least one or more of LaCuOS or LaCuOSe as its principal component, as well as to the manufacturing method thereof.
In recent years, a material having mainly oxychalcogenide containing La and Cu, in particular a material having at least one or more of LaCuOS or LaCuOSe as its principal component is known to be promising as a P-type transparent conductive material.
A P-type transparent conductive material of LaCuOS or LaCuOSe emits violet-blue light in a short wavelength near 400 nm. In other words, it is attracting attention as a violet-blue light emitting element (e.g., refer to “Room-Temperature excitons in wide-gap layered-oxysulfide semiconductor: LaCuOS” APPLIED PHYSICS LETTERS VOLUME 78, NUMBER 16, 16 Apr. 2001 and “Transparent P-Type Semiconductor: LaCuOS layered oxysulfide” APPLIED PHYSICS LETTERS VOLUME 77, NUMBER 17, 23 Oct. 2000).
The thin film of this kind of P-type transparent conductive material is usually formed with the laser abrasion method or sputtering method. The sputtering method is desirable in consideration of productivity. This sputtering method makes a positive electrode substrate and a negative electrode target face each other, and generates an electric field by applying a high voltage between the substrates thereof and the targets under an inert gas atmosphere. The sputtering method employs a fundamental principle where the inert gas are ionized, plasma which consists of electrons and the positive ion is formed, the positive ion in this plasma extrudes the atoms structuring the target by colliding with the target (negative electrode) surface, and the extruded atoms adhere to the opposing substrate surface, wherein the film is formed thereby.
These materials are deposited with a direct current (DC) sputtering device, radio-frequency wave sputtering (RF) device or magnetron sputtering device.
When preparing a sputtering target formed from a material having mainly oxychalcogenide containing La and Cu, the raw material powder thereof is usually sintered for such manufacture of the sputtering target. Nevertheless, the relative density is roughly 75% with the conventional sintering method, and there is a problem in that sufficient density cannot be obtained, and cracks will be generated during the sintering process as a result.
Further, conventionally, for example, even when sintering is performed for manufacturing a LaCuOS or LaCuOSe target having an even composition, there is a problem in that unreacted matter (e.g., La2O3), which is a part of the raw material component, will remain in addition to the foregoing components, and the uniformity of the components cannot be maintained.
Moreover, there are cases where the target would absorb moisture due to low density during its storage in the atmosphere, the target surface would deteriorate as a result of the reaction with water, and in certain cases a part of the target would peel off.
Due to the brittleness of the target, there is a problem in that it is difficult to manufacture a large target, and the deposition cost would increase in connection therewith. In addition, since unreacted matter would remain as described above, the material was once subject to calcination in a closed vessel, pulverized after this calcination, and the pulverized raw material was thereafter subject to sintering once again. Nevertheless, this process also incurred the problem of increased costs.
Further, generally speaking, the sputter face of the target can be made uniform and smooth by refining and densifying the crystal grains of the target, and this will also enable the reduction of particles and nodules as well as prolong the target life. Nevertheless, there is a problem in that the foregoing issues have not been sufficiently attended to.